the monitoring of vital signs plays a key role in the diagnosis of several diseases. piezoelectric sensors have been utilized to collect a corresponding representative signal from the chest surface. the subject typically needs to hold his or her breath to eliminate the respiration effect. This work further contributes to the extraction of the corresponding representative vital signs directly from the measured respiration signal. The contraction and expansion of the heart muscles, as well as the respiration activities, will induce a mechanical vibration across the chest wall. The induced vibration is then captured by the piezoelectric sensor placed at the chest surface, which produces an electrical output voltage signal conformally mapped with the respiration-cardiac activities. During breathing, the measured voltage signal is composed of the cardiac cycle activities modulated along with the respiratory cycle activity. A representative model that incorporates the cardiac and respiratory activities is developed and adopted. The piezoelectric and the convolution theories along with Fourier transformation are applied to extract the corresponding cardiac activity signal from the respiration signal. All the results were validated step by step by a conventional apparatus, with good agreement observed. Monitoring vital signs is essential for daily health and medical diagnosis 1. Vital signs, such as electrocardiogram (ECG) measurements, heart rate 2 , respiration rate 3 , systolic pressure (SP), and diastolic pressure (DP) 4 , along with pressure pulse play an important role in determining the state of health of a subject 5. Various methods and systems have recently been developed to monitor such vital signs 6-12. These vital signs are extracted from the acquired signals that enable more effective safeguarding of health by allowing for the early detection of any disease or abnormality 13-15. Researchers have recently focused on developing a remote non-contact sensing system having the ability to perform accurate long-term continuous monitoring of human vital signs. Measuring vital signs (such as respiration rates, blood pressure, and heart rates) continuously and remotely without touching the patients can be an invaluable tool for physicians, as it can be used to make life-and-death decisions rapidly and make better decisions when long-term patient data are available 16. The systems used to monitor vital signs may prevent diseases and enhance quality of life, thus reducing the costs of health care 17. Noninvasive vital sign monitoring, which includes measurement of pulse oximetry 18 , capnography, blood pressure (BP) measurement, and the standard five-lead electrocardiogram 19 , has been used for patients who are in the intensive care unit 20 and in the operating room. A stepped frequency continuous wave (SFCW) radar is also used to measure the heart rate and respiration by transmitting high average power pulses with long duration and narrow bandwidth, then a signal-processing algorithm based on the state space method is...
The piezoelectric materials are incorporated in smart structure to exhibit specific functionality. The activity of piezoelectric material dimension and electrical properties can be changed with an applied stress. These variations are translated to a change in the capacitance of the structure. This work takes a close outlook on the use of the capacitance-voltage measurements for the extraction of double piezoelectric thin film material deposited at the two faces of a flexible steel sheet. The piezoelectric thin film materials have been deposited using RF sputtering techniques. Gamry analyzer references 3000 was used to collect the capacitance-voltage measurements from both layers. The developed algorithm extracts directly the piezoelectric coefficients knowing the film thickness, the applied voltage, and the capacitance ratio. The capacitance ratio is the ratio between the capacitances of the film when the applied field in antiparallel and parallel to the polling field direction, respectively. The method has been calibrated using a piezoelectric bulk ceramic and validated by comparing the result with the reported values in the literature. The extracted values using the current approach match well the values extracted by other existing methods.
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